I can't figure out how to change the size of rooms or create damage or hp of objects. The damage and hp I would guess would have something to do with private variables (or attributes, can't remember) but I couldn't figure anything out. Plus, once I made hp or damage, how would I apply them with events?

In the Project bar on the right of your screen you'll see "Layout 1" or similar, and you can click that to bring its properties up in the "Properties" bar on the left for you to edit. You then edit its width and height as-needed.